#include <stdio.h>

char *polacz(char* a, char* b)
{
    int len = strlen(a) + strlen(b);

    char* str = (char*)malloc(len + 1);

    int i, l;

    for (i = 0; i < strlen(a); i++) {
        str[i] = a[i];
    }
    int t = 0;

    for (l = strlen(a); l <= len; l++) {
        str[l] = b[t];
        t++;
    }

    return str;
}


int main()
{
    char pierwszy[] = "start";
    char drugi[]    = "koniec";
    char *cos = polacz(drugi, pierwszy);

    printf("%s\n", cos);

    getchar();
    return 0;
}